The present invention relates to a microwave oven, and more particularly to a microwave oven capable of preventing overcurrent of a microswitch for controlling a DC power source, which is capable of being prevented from holding the previous status of contacts in a microswitch caused by the large amounts of current which are remaining when usig direct current.
FIG. 1 shows a microwave oven for heating/cooking food using microwaves. The microwave oven contains a case 20 for forming a cooking chamber 22, a door 21 for opening/closing the cooking chamber 22, a tray 24 being installed in the cooking chamber 22, and a panel 25 for controlling operations of the microwave oven.
FIG. 2 is a partial cutaway view of FIG. 1. A pair of latch hooks 28a, 28b are installed in the door 21, and catch openings 27a, 27b are formed corresponding to each latch hook 28a, 28b at a front plate 26 of the case 20. If the door 21 is pushed shut, the latch hooks 28a, 28b will engage the catch openings 27a, 27b to hold the door 21 shut.
At the back side of the panel 25 is provided a device chamber (not shown). In the device chamber are installed a magnetron for generating microwaves and a high voltage transformer HVT for generating a high voltage supplied to the magnetron, and so on. In supplying an AC power to the high voltage transformer HVT, this high voltage transformer HVT generates a predetermined high voltage to drive the magnetron. Then, the magnetron radiates microwaves of about 2,450 MHz frequency to heat/cook food.
As shown in FIG. 2, microswitches MS1, MS2, MS3 are installed at the back side of the front plate 26 of the case 20. FIGS. 3a, and 3b are schematic diagrams and symbols of each microswitch MS1, MS2, MS3, respectively. The microswitches MS1, MS2, MS3 have a slight interval at the contacts, and a mechanism of a snap action. The microswitches MS1, MS2, MS3 have a contact mechanism to open/close by the determined operation and force in a sealing case, and is a small switch for arranging a pushing mechanism of the actuator switch located on the outside of the case. That is, the microswitch is one of the contact type detectors, which detects something contacted according to releasing the inside contacts when something 6 closes to a push button 1, and begins to push the push button 1, and applies more than a predetermined force F to the push button 1. In FIG. 3, the reference numeral 2 is a movable spring, and the reference numeral 3 is a movable contact. The reference numeral 4 is a fixed contact b, and the reference numeral 5 is a fixed contact a. COM, NO, and NC are a common terminal, a normally open terminal, and a normally closed terminal, respectively. In FIG. 3b, the contact a 7 is a point of contact which conducts first when the microswitch is operated, and which connects the common terminal COM into the normally open terminal NO. The contact b 7 is a point of contact which conducts when the microswitch is not operated, and which connects the common terminal COM into the normally close terminal NC.
The microswitches MS1, MS2, MS3 have each operating button 31, 32, 33, respectively. At the back side of the front plate 26 are installed a pair of movable members 29a, 29b to adjoin the catch openings 27a, 27b. Then, the movable members 29a, 29b are fixed for pivoting by each pin 23a, 23b, and are fixed elastically by each spring 41a, 41b. 
In FIG. 2, if the door 21 is pushed close, the microswitches MS1, MS2, MS3 are operated by the latch hooks 28a, 28b which are inserted in the catch openings 27a, 27b. That is, when the movable members 29a, 29b are pushed by each latch hook 28a, 28b, the movable members 29a, 29b are rotated against the elasticity of the springs 41a, 41b. Therefore, the operating button 31 is pushed by the upper movable members 29a, and the operating buttons 32, 33 are pushed by the lower movable members 29b, respectively.
Meanwhile, since the conventional microwave oven has been made to be operated using the AC common power source of 110V/220V for supplying high alternating current, we cannot use the microwave oven in a place where alternating current is not available.
To overcome the above described problem, an AC/DC type microwave oven has been developed, and has been comprised as shown in FIG. 4. In FIG. 4, An AC/DC type microwave oven comprises an AC driving load 30, a DC driving load and DC/AC converting part 40, and a microwave oscillator 50. The AC driving load 30 is driven by an AC input power. The DC driving load and DC/AC converting part 40 includes the DC driving load being driven by a DC input power, and the DC/AC converter converting the DC input power into an AC power. The microwave oscillator 50 is supplied by only one of the AC input power or the DC/AC power converted by a DC/AC converter, and generates microwaves.
The AC driving load 30 is driven by alternating current, which includes a lamp and a fan motor, etc., which are connected to the AC power source. A power switch (not shown) to determine the supplying status of AC is connected to the AC power source. The DC driving load being driven by direct current, which includes a lamp and a fan motor, etc., which are connected to the DC power source. A power switch (not shown) to determine the supplying status of DC is connected to the DC power source. The direct current forms a differentiated DC circuit net discriminated as an AC circuit net. Then, direct current is connected to the input side of the DC/AC converting part 40 which supplies alternating current. The microwave oscillating part 50 includes a high voltage transformer HVT which receives the AC power, a high voltage condenser HVC, a high voltage diode HVD, and a magnetron MGT. The operation of the microwave oscillating part 50 is described the same way as shown in FIG. 1.
Therefore, according as the AC power source supplies alternating current to the AC driving load 30, and the DC power source supplies direct current to the DC driving load and DC/AC converting part 40, respectively, the conventional AC/DC type microwave oven is operated.
In the above-described AC/DC type microwave oven, the DC driving load and DC/AC converting part 40 is designed for the user to use the AC/DC type microwave oven out-of-doors, using the power source of an automobile battery. Generally, however, the common AC power source supplies small amounts of current within 15A, but the battery of the automobile using DC supplies large amounts of current from 50A to 70A.
If the microwave oven is operated by using the automobile battery, the microswitches MS1, MS2 have the possibility of a faulty operation.
That is, in case the large amounts of current is supplied through the microswitches MS1, MS2, the contact of the microswitches MS1, MS2 can remain in there contacting status. When the user pulls the door 21 so that the cooking chamber is open, the operating buttons 31, 32 of the microswitches MS1, MS2 can remain in their depressed status. According as the primary switch PD and secondary switch SD of the DC driving load and DC/AC converting part 40 are held in their closed status, and then current is supplied to the DC driving load and DC/AC converting part 40, so the AC/DC type microwave oven has the problem of encountering a malfunction.
The present invention has been made to overcome the problems with microwave ovens described in the foregoing paragraphs, and accordingly it is the first objective of the present invention to provide a microwave oven capable of preventing overcurrent of a microswitch for controlling a DC power source.
It is the second objective of the present invention to provide a microwave oven for heating/cooking food safely by preventing overcurrent of a microswitch for controlling a DC power source.
To achieve the above objectives, the present invention provides a microwave oven capable of preventing overcurrent of a microswitch for controlling a DC power source. In a microwave oven having a case forming a cooking chamber, a door for opening/closing the chamber, a high voltage transformer for generating a high voltage, and a magnetron for generating microwaves driven by the high voltage being outputted from the high voltage transformer, a microwave oven comprising: means for detecting opening/closing of the door; means for controlling for outputting a driving signal corresponding to the detected result; and means for opening/closing for controlling a power source supplied to the high voltage transformer according to receiving the driving signal.
The means for detecting is a microswitch which is a detector for detecting the openinig/closing of the door.
The means for opening/closing is an electromagnetic relay for controlling an opening/closing of an input power source to open/close a contact according to the driving signal, wherein the relay is an electromagnetic relay for controlling a supply of large amounts of current from 50A to 70A.
To achieve the above objectives, the present invention provides an interlock device of a microwave oven. In a microwave oven having a case forming a cooking chamber, a door for opening/closing the chamber, a high voltage transformer for generating a high voltage, and a magnetron for generating microwaves driven by the high voltage being outputted from the high voltage transformer, an interlocking device of a microwave oven comprising: microswitches for detecting opening/closing of the door; microcomputer for outputting a driving signal corresponding to the detected result; and a relay for opening/closing for controlling a power source supplied to the high voltage transformer according to receiving the driving signal.
The relay is an electromagnetic relay for controlling a supply of large amounts of current from 50A to 70A.
To achieve the above objectives, the present invention provides a microwave oven capable of preventing overcurrent of a microswitch for controlling a DC power source. In a microwave oven using microwaves, the microwave oven comprising: a DC circuit part for converting direct current supplied by a DC input power source into alternating current, and for supplying the converted alternating current; an opening/closing means for connecting between the DC input power source and the DC circuit part; a current dividing means being connected to the means for opening/closing, and for dividing a part of current supplied by the means for opening/closing when the means for opening/closing is switched on; and a microwave oscillating means for being driven by an output voltage of the high voltage transformer, and for generating microwaves.
The current dividing means is a relay connected to the opening/closing means in parallel. The present invention further comprises resistors for being connected to the opening/closing means and/or the relay current dividing means in series, respectively, and for regulating each rate of current through the opening/closing means and the relay, respectively.
To achieve the above objectives, the present invention provides a device for preventing overcurrent of a microswitch comprising: a microswitch for opening/closing the connection between DC input power source and a DC circuit part being supplied direct current; and a current dividing means being connected to the microswitch in parallel, and for dividing a part of current through the microswitch when the microswitch is switched on.
According to the present invention, a microwave oven is capable of preventing overcurrent of a microswitch by using a relay, and so on. A microwave oven can be heating/cooking food safely according to being prevented from a holding of the previous status of contacts in a microswitch by preventing overcurrent of a microswitch for controlling a DC power source.